Closed-form representation for equivalent electromagnetic parameters of biaxial anisotropic honeycomb absorbing materials

A closed-form representation for equivalent electromagnetic parameters (EEP) of biaxial anisotropic honeycomb absorbing materials (HAM) is proposed based on long-wavelength approximation. Considering the specific physical parameters such as the side length of aramid paper honeycomb, the thickness of aramid paper honeycomb, the thickness of absorbing coating and the height of honeycomb absorbing material, the closed-form representation for its equivalent electromagnetic parameter is established and obtained. The correctness and effectiveness of the closed-form representation are verified by numerical simulation and experimental tests. The numerical simulation uses the finite time domain difference method combined with the Nicholson–Ross–Weir (NRW) method. The EEP of the anisotropic HAM calculated by the closed-form representation are more accurate than obtained by the NRW method. The honeycomb absorbing material was prepared by the immersion process, and the reflectance measured by the free space method was consistent with the reflectance calculated by the closed-form representation proposed in this paper within 2–18 GHz. The proposed closed-form representation for equivalent electromagnetic parameter of biaxial anisotropic HAM shows the biaxial anisotropic characteristics of HAM. At the same time, the new model has the advantages of simple principle, convenient use, high precision and frequency bandwidth, which may provide more accurate theoretical guidance for the design of HAM.